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      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Index File Formats"><strong>Index File Formats</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                This document defines the index file formats used
                in Lucene version 1.4.
            </p>
                                                <p>
                Jakarta Lucene is written in Java, but several
                efforts are underway to write versions of Lucene in other programming
                languages.  If these versions are to remain compatible with Jakarta
                Lucene, then a language-independent definition of the Lucene index
                format is required.  This document thus attempts to provide a
                complete and independent definition of the Jakarta Lucene 1.4 file
                formats.
            </p>
                                                <p>
                As Lucene evolves, this document should evolve.
                Versions of Lucene in different programming languages should endeavor
                to agree on file formats, and generate new versions of this document.
            </p>
                                                <p>
                Compatibility notes are provided in this document,
                describing how file formats have changed from prior versions.
            </p>
                            </blockquote>
        </p>
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          <a name="Definitions"><strong>Definitions</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                The fundamental concepts in Lucene are index,
                document, field and term.
            </p>
                                                <p>
                An index contains a sequence of documents.
            </p>
                                                <ul>
                <li>
                    <p>
                        A document is a sequence of fields.
                    </p>
                </li>

                <li>
                    <p>
                        A field is a named sequence of terms.
                    </p>
                </li>

                <li>
                    A term is a string.
                </li>
            </ul>
                                                <p>
                The same string in two different fields is
                considered a different term.  Thus terms are represented as a pair of
                strings, the first naming the field, and the second naming text
                within the field.
            </p>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Inverted Indexing"><strong>Inverted Indexing</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The index stores statistics about terms in order
                    to make term-based search more efficient.  Lucene's
                    index falls into the family of indexes known as an <i>inverted
                        index.</i> This is because it can list, for a term, the documents that contain
                    it.  This is the inverse of the natural relationship, in which
                    documents list terms.
                </p>
                            </blockquote>
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      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Types of Fields"><strong>Types of Fields</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    In Lucene, fields may be <i>stored</i>, in which
                    case their text is stored in the index literally, in a non-inverted
                    manner.  Fields that are inverted are called <i>indexed</i>. A field
                    may be both stored and indexed.</p>
                                                <p>The text of a field may be <i>tokenized</i> into terms to be
                    indexed, or the text of a field may be used literally as a term to be indexed.
                    Most fields are
                    tokenized, but sometimes it is useful for certain identifier fields
                    to be indexed literally.
                </p>
                            </blockquote>
      </td></tr>
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                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Segments"><strong>Segments</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    Lucene indexes may be composed of multiple sub-indexes, or<i>
                        segments</i>. Each segment is a fully independent index, which could be searched
                    separately. Indexes evolve by:
                </p>
                                                <ol>
                    <li><p>Creating new segments for newly added documents.</p>
                    </li>
                    <li><p>Merging existing segments.</p>
                    </li>
                </ol>
                                                <p>
                    Searches may involve multiple segments and/or multiple indexes, each
                    index potentially composed of a set of segments.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Document Numbers"><strong>Document Numbers</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    Internally, Lucene refers to documents by an integer <i>document
                        number</i>. The first document added to an index is numbered zero, and each
                    subsequent document added gets a number one greater than the previous.
                </p>
                                                <p>
                    <br />
                </p>
                                                <p>
                    Note that a document's number may change, so caution should be taken
                    when storing these numbers outside of Lucene.  In particular, numbers may
                    change in the following situations:
                </p>
                                                <ul>
                    <li>
                        <p>
                            The
                            numbers stored in each segment are unique only within the segment,
                            and must be converted before they can be used in a larger context.
                            The standard technique is to allocate each segment a range of
                            values, based on the range of numbers used in that segment.  To
                            convert a document number from a segment to an external value, the
                            segment's <i>base</i> document
                            number is added.  To convert an external value back to a
                            segment-specific value, the  segment is identified by the range that
                            the external value is in, and the segment's base value is
                            subtracted.  For example two five document segments might be
                            combined, so that the first segment has a base value of zero, and
                            the second of five.  Document three from the second segment would
                            have an external value of eight.
                        </p>
                    </li>
                    <li>
                        <p>
                            When documents are deleted, gaps are created
                            in the numbering.  These are eventually removed as the index evolves
                            through merging.  Deleted documents are dropped when segments are
                            merged.  A freshly-merged segment thus has no gaps in its numbering.
                        </p>
                    </li>
                </ul>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Overview"><strong>Overview</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                Each segment index maintains the following:
            </p>
                                                <ul>
                <li><p>Field names.  This
                        contains the set of field names used in the index.

                    </p>
                </li>
                <li><p>Stored Field
                        values.  This contains, for each document, a list of attribute-value
                        pairs, where the attributes are field names.  These are used to
                        store auxiliary information about the document, such as its title,
                        url, or an identifier to access a
                        database. The set of stored fields are what is returned for each hit
                        when searching.  This is keyed by document number.
                    </p>
                </li>
                <li><p>Term dictionary.
                        A dictionary containing all of the terms used in all of the indexed
                        fields of all of the documents.  The dictionary also contains the
                        number of documents which contain the term, and pointers to the
                        term's frequency and proximity data.
                    </p>
                </li>

                <li><p>Term Frequency
                        data.  For each term in the dictionary, the numbers of all the
                        documents that contain that term, and the frequency of the term in
                        that document.
                    </p>
                </li>

                <li><p>Term Proximity
                        data.  For each term in the dictionary, the positions that the term
                        occurs in each document.
                    </p>
                </li>

                <li><p>Normalization
                        factors.  For each field in each document, a value is stored that is
                        multiplied into the score for hits on that field.
                    </p>
                </li>
                <li><p>Term Vectors.  For each field in each document, the term vector
                       (sometimes called document vector) is stored.  A term vector consists
                       of term text and term frequency.
                    </p>
                </li>              
                <li><p>Deleted documents.
                        An optional file indicating which documents are deleted.
                    </p>
                </li>
            </ul>
                                                <p>Details on each of these are provided in subsequent sections.
            </p>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="File Naming"><strong>File Naming</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                All files belonging to a segment have the same name with varying
                extensions.  The extensions correspond to the different file formats
                described below.
            </p>
                                                <p>
                Typically, all segments
                in an index are stored in a single directory, although this is not
                required.
            </p>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Primitive Types"><strong>Primitive Types</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                        <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Byte"><strong>Byte</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The most primitive type
                    is an eight-bit byte.  Files are accessed as sequences of bytes.  All
                    other data types are defined as sequences
                    of bytes, so file formats are byte-order independent.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="UInt32"><strong>UInt32</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    32-bit unsigned integers are written as four
                    bytes, high-order bytes first.
                </p>
                                                <p>
                    UInt32    --&gt; &lt;Byte&gt;<sup>4</sup>
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Uint64"><strong>Uint64</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    64-bit unsigned integers are written as eight
                    bytes, high-order bytes first.
                </p>
                                                <p>UInt64    --&gt; &lt;Byte&gt;<sup>8</sup>
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="VInt"><strong>VInt</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    A variable-length format for positive integers is
                    defined where the high-order bit of each byte indicates whether more
                    bytes remain to be read.  The low-order seven bits are appended as
                    increasingly more significant bits in the resulting integer value.
                    Thus values from zero to 127 may be stored in a single byte, values
                    from 128 to 16,383 may be stored in two bytes, and so on.
                </p>
                                                <p><b>VInt Encoding Example</b></p>
                                                <table>
                                                                        <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT"><b>Value</b>
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT"><b>First byte</b>
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT"><b>Second byte</b>
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT"><b>Third byte</b>
                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">0
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                00000000
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">1
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">2
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                00000010
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">...
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: 0.11cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">127
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                01111111
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">128
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                10000000
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">129
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                10000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">130
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                10000010
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">...
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: 0.11cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.07cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">16,383
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                11111111
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                01111111
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT" style="margin-left: -0.47cm; margin-right:                                0.01cm"><br />

                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">16,384
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                10000000
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                10000000
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.47cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">16,385
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                10000001
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                10000000
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.47cm;                                margin-right: 0.01cm">
                                00000001
                            </p>
                        
            </font>
</td>
            </tr>
                                <tr>
                        <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p align="RIGHT">...
                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: 0.11cm;                                margin-right: 0.01cm">
                                <br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.07cm;                                margin-right: 0.01cm">
                                <br />

                            </p>
                        
            </font>
</td>
                                <td bgcolor="#a0ddf0" colspan="" rowspan="" valign="top" align="left">
    <font color="#000000" size="-1" face="arial,helvetica,sanserif">
                
                            <p class="western" align="RIGHT" style="margin-left: -0.47cm;                                margin-right: 0.01cm">
                                <br />

                            </p>
                        
            </font>
</td>
            </tr>
            </table>
                                                <p>
                    This provides compression while still being
                    efficient to decode.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Chars"><strong>Chars</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    Lucene writes unicode
                    character sequences using the standard UTF-8 encoding.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="String"><strong>String</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    Lucene writes strings as a VInt representing the length, followed by
                    the character data.
                </p>
                                                <p>
                    String --&gt; VInt, Chars
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Per-Index Files"><strong>Per-Index Files</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                The files in this section exist one-per-index.
            </p>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Segments File"><strong>Segments File</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The active segments in the index are stored in the
                    segment info file.  An index only has
                    a single file in this format, and it is named "segments".
                    This lists each segment by name, and also contains the size of each
                    segment.
                </p>
                                                <p>
                    Segments    --&gt; Format, Version, SegCount, &lt;SegName, SegSize&gt;<sup>SegCount</sup>
                </p>
                                                <p>
                    Format, SegCount, SegSize    --&gt; UInt32
                </p>
                                                <p>
                    Version --&gt; UInt64
                </p>
                                                <p>
                    SegName    --&gt; String
                </p>
                                                <p>
                    Format is -1 in Lucene 1.4.
                </p>
                                                <p>
                    Version counts how often the index has been
                    changed by adding or deleting documents.
                </p>
                                                <p>
                    SegName is the name of the segment, and is used as the file name prefix
                    for all of the files that compose the segment's index.
                </p>
                                                <p>
                    SegSize is the number of documents contained in the segment index.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Lock Files"><strong>Lock Files</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    Several files are used to indicate that another
                    process is using an index.  Note that these files are not
                    stored in the index directory itself, but rather in the
                    system's temporary directory, as indicated in the Java
                    system property "java.io.tmpdir".
                </p>
                                                <ul>
                    <li>
                        <p>
                            When a file named "commit.lock"
                            is present, a process is currently re-writing the "segments"
                            file and deleting outdated segment index files, or a process is
                            reading the "segments"
                            file and opening the files of the segments it names.  This lock file
                            prevents files from being deleted by another process after a process
                            has read the "segments"
                            file but before it has managed to open all of the files of the
                            segments named therein.
                        </p>
                    </li>

                    <li>
                        <p>
                            When a file named "write.lock"
                            is present, a process is currently adding documents to an index, or
                            removing files from that index.  This lock file prevents several
                            processes from attempting to modify an index at the same time.
                        </p>
                    </li>
                </ul>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Deletable File"><strong>Deletable File</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    A file named "deletable"
                    contains the names of files that are no longer used by the index, but
                    which could not be deleted.  This is only used on Win32, where a
                    file may not be deleted while it is still open. On other platforms
                    the file contains only null bytes.
                </p>
                                                <p>
                    Deletable    --&gt; DeletableCount,
                    &lt;DelableName&gt;<sup>DeletableCount</sup>
                </p>
                                                <p>DeletableCount    --&gt; UInt32
                </p>
                                                <p>DeletableName    --&gt;
                    String
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Per-Segment Files"><strong>Per-Segment Files</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                The remaining files are all per-segment, and are
                thus defined by suffix.
            </p>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Fields"><strong>Fields</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p><br /><b>Field Info</b><br /></p>
                                                <p>
                    Field names are
                    stored in the field info file, with suffix .fnm.
                </p>
                                                <p>
                    FieldInfos
                    (.fnm)    --&gt; FieldsCount, &lt;FieldName,
                    FieldBits&gt;<sup>FieldsCount</sup>
                </p>
                                                <p>
                    FieldsCount    --&gt; VInt
                </p>
                                                <p>
                    FieldName    --&gt; String
                </p>
                                                <p>
                    FieldBits    --&gt; Byte
                </p>
                                                <p>
                    The low-order bit is one for
                    indexed fields, and zero for non-indexed fields.  The second lowest-order
                    bit is one for fields that have term vectors stored, and zero for fields
                    without term vectors.
                </p>
                                                <p>
                    Fields are numbered by their order in this file.  Thus field zero is
                    the
                    first field in the file, field one the next, and so on.  Note that,
                    like document numbers, field numbers are segment relative.
                </p>
                                                <p><br /><b>Stored Fields</b><br /></p>
                                                <p>
                    Stored fields are represented by two files:
                </p>
                                                <ol>
                    <li>
                        <p>
                            The field index, or .fdx file.
                        </p>

                        <p>
                            This contains, for each document, a pointer to
                            its field data, as follows:
                        </p>

                        <p>
                            FieldIndex
                            (.fdx)    --&gt;
                            &lt;FieldValuesPosition&gt;<sup>SegSize</sup>
                        </p>
                        <p>FieldValuesPosition
                            --&gt; Uint64
                        </p>
                        <p>This
                            is used to find the location within the field data file of the
                            fields of a particular document.  Because it contains fixed-length
                            data, this file may be easily randomly accessed.  The position of
                            document<i> n</i>'s<i> </i>field data is the Uint64 at <i>n*8</i> in
                            this file.
                        </p>
                    </li>
                    <li>
                        <p>
                            The field data, or .fdt file.

                        </p>

                        <p>
                            This contains the stored fields of each document,
                            as follows:
                        </p>

                        <p>
                            FieldData (.fdt)    --&gt;
                            &lt;DocFieldData&gt;<sup>SegSize</sup>
                        </p>
                        <p>DocFieldData    --&gt;
                            FieldCount, &lt;FieldNum, Bits, Value&gt;<sup>FieldCount</sup>
                        </p>
                        <p>FieldCount  --&gt;
                            VInt
                        </p>
                        <p>FieldNum    --&gt;
                            VInt
                        </p>
                        <p>Bits        --&gt;
                            Byte
                        </p>
                        <p>Value        --&gt;
                            String
                        </p>
                        <p>Currently
                            only the low-order bit is used of Bits is used.  It is one for
                            tokenized fields, and zero for non-tokenized fields.
                        </p>
                    </li>
                </ol>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Term Dictionary"><strong>Term Dictionary</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The term dictionary is represented as two files:
                </p>
                                                <ol>
                    <li>
                        <p>
                            The term infos, or tis file.
                        </p>

                        <p>
                            TermInfoFile (.tis)--&gt;
                            TIVersion, TermCount, IndexInterval, SkipInterval, TermInfos
                        </p>
                        <p>TIVersion    --&gt;
                            UInt32
                        </p>
                        <p>TermCount    --&gt;
                            UInt64
                        </p>
                        <p>IndexInterval    --&gt;
                            UInt32
                        </p>
                        <p>SkipInterval   --&gt;
                            UInt32
                        </p>
                        <p>TermInfos    --&gt;
                            &lt;TermInfo&gt;<sup>TermCount</sup>
                        </p>
                        <p>TermInfo    --&gt;
                            &lt;Term, DocFreq, FreqDelta, ProxDelta, SkipDelta&gt;
                        </p>
                        <p>Term        --&gt;
                            &lt;PrefixLength, Suffix, FieldNum&gt;
                        </p>
                        <p>Suffix        --&gt;
                            String
                        </p>
                        <p>PrefixLength,
                            DocFreq, FreqDelta, ProxDelta, SkipDelta<br />        --&gt; VInt
                        </p>
                        <p>This
                            file is sorted by Term.  Terms are ordered first lexicographically
                            by the term's field name, and within that lexicographically by the
                            term's text.
                        </p>
                        <p>TIVersion names the version of the format
                            of this file and is -2 in Lucene 1.4.
                        </p>
                        <p>Term
                            text prefixes are shared.  The PrefixLength is the number of initial
                            characters from the previous term which must be pre-pended to a
                            term's suffix in order to form the term's text.  Thus, if the
                            previous term's text was "bone" and the term is "boy",
                            the PrefixLength is two and the suffix is "y".
                        </p>
                        <p>FieldNumber
                            determines the term's field, whose name is stored in the .fdt file.
                        </p>
                        <p>DocFreq
                            is the count of documents which contain the term.
                        </p>
                        <p>FreqDelta
                            determines the position of this term's TermFreqs within the .frq
                            file.  In particular, it is the difference between the position of
                            this term's data in that file and the position of the previous
                            term's data (or zero, for the first term in the file).
                        </p>
                        <p>ProxDelta
                            determines the position of this term's TermPositions within the .prx
                            file.  In particular, it is the difference between the position of
                            this term's data in that file and the position of the previous
                            term's data (or zero, for the first term in the file.
                        </p>
                        <p>SkipDelta determines the position of this
                            term's SkipData within the .frq file.  In
                            particular, it is the number of bytes
                            after TermFreqs that the SkipData starts.
                            In other words, it is the length of the
                            TermFreq data.
                        </p>
                    </li>
                    <li>
                        <p>
                            The term info index, or .tii file.
                        </p>

                        <p>
                            This contains every IndexInterval<sup>th</sup> entry from the .tis
                            file, along with its location in the "tis" file.  This is
                            designed to be read entirely into memory and used to provide random
                            access to the "tis" file.
                        </p>

                        <p>
                            The structure of this file is very similar to the
                            .tis file, with the addition of one item per record, the IndexDelta.
                        </p>

                        <p>
                            TermInfoIndex (.tii)--&gt;
                            IndexTermCount, TermIndices
                        </p>
                        <p>IndexTermCount    --&gt;
                            UInt32
                        </p>
                        <p>TermIndices    --&gt;
                            &lt;TermInfo, IndexDelta&gt;<sup>IndexTermCount</sup>
                        </p>
                        <p>IndexDelta    --&gt;
                            VInt
                        </p>
                        <p>IndexDelta
                            determines the position of this term's TermInfo the .tis file.  In
                            particular, it is the difference between the position of this term's
                            entry in that file and the position of the previous term's entry (or
                            zero for the first term in the file).
                        </p>
                    </li>
                </ol>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Frequencies"><strong>Frequencies</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The .frq file contains the lists of documents
                    which contain each term, along with the frequency of the term in that
                    document.
                </p>
                                                <p>FreqFile (.frq)    --&gt;
                    &lt;TermFreqs, SkipData&gt;<sup>TermCount</sup>
                </p>
                                                <p>TermFreqs    --&gt;
                    &lt;TermFreq&gt;<sup>DocFreq</sup>
                </p>
                                                <p>TermFreq        --&gt;
                    DocDelta, Freq?
                </p>
                                                <p>SkipData        --&gt;
                    &lt;SkipDatum&gt;<sup>DocFreq/SkipInterval</sup>
                </p>
                                                <p>SkipDatum    --&gt;
                    DocSkip,FreqSkip,ProxSkip
                </p>
                                                <p>DocDelta,Freq,DocSkip,FreqSkip,ProxSkip    --&gt;
                    VInt
                </p>
                                                <p>TermFreqs
                    are ordered by term (the term is implicit, from the .tis file).
                </p>
                                                <p>TermFreq
                    entries are ordered by increasing document number.
                </p>
                                                <p>DocDelta
                    determines both the document number and the frequency.  In
                    particular, DocDelta/2 is the difference between this document number
                    and the previous document number (or zero when this is the first
                    document in a TermFreqs).  When DocDelta is odd, the frequency is
                    one.  When DocDelta is even, the frequency is read as another VInt.
                </p>
                                                <p>For
                    example, the TermFreqs for a term which occurs once in document seven
                    and three times in document eleven would be the following sequence of
                    VInts:
                </p>
                                                <p>    15,
                    22, 3
                </p>
                                                <p>DocSkip records the document number before every
                    SkipInterval<sup>th</sup> document in TermFreqs.
                    Document numbers are represented as differences
                    from the previous value in the sequence.  FreqSkip
                    and ProxSkip record the position of every
                    SkipInterval<sup>th</sup> entry in FreqFile and
                    ProxFile, respectively.  File positions are
                    relative to the start of TermFreqs and Positions,
                    to the previous SkipDatum in the sequence.
                </p>
                                                <p>For example, if DocFreq=35 and SkipInterval=16,
                    then there are two SkipData entries, containing
                    the 15<sup>th</sup> and 31<sup>st</sup> document
                    numbers in TermFreqs.  The first FreqSkip names
                    the number of bytes after the beginning of
                    TermFreqs that the 16<sup>th</sup> SkipDatum
                    starts, and the second the number of bytes after
                    that that the 32<sup>nd</sup> starts.  The first
                    ProxSkip names the number of bytes after the
                    beginning of Positions that the 16<sup>th</sup>
                    SkipDatum starts, and the second the number of
                    bytes after that that the 32<sup>nd</sup> starts.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Positions"><strong>Positions</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>
                    The .prx file contains the lists of positions that
                    each term occurs at within documents.
                </p>
                                                <p>ProxFile (.prx)    --&gt;
                    &lt;TermPositions&gt;<sup>TermCount</sup>
                </p>
                                                <p>TermPositions    --&gt;
                    &lt;Positions&gt;<sup>DocFreq</sup>
                </p>
                                                <p>Positions        --&gt;
                    &lt;PositionDelta&gt;<sup>Freq</sup>
                </p>
                                                <p>PositionDelta    --&gt;
                    VInt
                </p>
                                                <p>TermPositions
                    are ordered by term (the term is implicit, from the .tis file).
                </p>
                                                <p>Positions
                    entries are ordered by increasing document number (the document
                    number is implicit from the .frq file).
                </p>
                                                <p>PositionDelta
                    is the difference between the position of the current occurrence in
                    the document and the previous occurrence (or zero, if this is the
                    first occurrence in this document).
                </p>
                                                <p>
                    For example, the TermPositions for a
                    term which occurs as the fourth term in one document, and as the
                    fifth and ninth term in a subsequent document, would be the following
                    sequence of VInts:
                </p>
                                                <p>    4,
                    5, 4
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Normalization Factors"><strong>Normalization Factors</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>There's a norm file for each indexed field with a byte for
                   each document.  The .f[0-9]* file contains,
                    for each document, a byte that encodes a value that is multiplied
                    into the score for hits on that field:
                </p>
                                                <p>Norms
                    (.f[0-9]*)    --&gt; &lt;Byte&gt;<sup>SegSize</sup>
                </p>
                                                <p>Each
                    byte encodes a floating point value.  Bits 0-2 contain the 3-bit
                    mantissa, and bits 3-8 contain the 5-bit exponent.
                </p>
                                                <p>These
                    are converted to an IEEE single float value as follows:
                </p>
                                                <ol>
                    <li><p>If
                            the byte is zero, use a zero float.
                        </p>
                    </li>
                    <li><p>Otherwise,
                            set the sign bit of the float to zero;
                        </p>
                    </li>
                    <li><p>add
                            48 to the exponent and use this as the float's exponent;
                        </p>
                    </li>
                    <li><p>map
                            the mantissa to the high-order 3 bits of the float's mantissa; and

                        </p>
                    </li>
                    <li><p>set
                            the low-order 21 bits of the float's mantissa to zero.
                        </p>
                    </li>
                </ol>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Term Vectors"><strong>Term Vectors</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <ol>
                <li>
                  <p>The Document Index or .tvx file.</p>
                  <p>This contains, for each document, a pointer to the document data in the Document 
                    (.tvd) file.
                  </p>
                  <p>DocumentIndex (.tvx) --&gt; TVXVersion&lt;DocumentPosition&gt;<sup>NumDocs</sup></p>
                  <p>TVXVersion --&gt; Int</p>
                  <p>DocumentPosition   --&gt; UInt64</p>
                  <p>This is used to find the position of the Document in the .tvd file.</p>
                </li>
                <li>
                  <p>The Document or .tvd file.</p>
                  <p>This contains, for each document, the number of fields, a list of the fields with
                  term vector info and finally a list of pointers to the field information in the .tvf 
                  (Term Vector Fields) file.</p>
                  <p>
                    Document (.tvd) --&gt; TVDVersion&lt;NumFields, FieldNums, FieldPositions,&gt;<sup>NumDocs</sup>
                  </p>
                  <p>TVDVersion --&gt; Int</p>
                  <p>NumFields --&gt; VInt</p>
                  <p>FieldNums --&gt; &lt;FieldNumDelta&gt;<sup>NumFields</sup></p>
                  <p>FieldNumDelta --&gt; VInt</p>
                  <p>FieldPositions --&gt; &lt;FieldPosition&gt;<sup>NumFields</sup></p>
                  <p>FieldPosition --&gt; VLong</p>
                  <p>The .tvd file is used to map out the fields that have term vectors stored and
                  where the field information is in the .tvf file.</p>
                </li>
                <li>
                  <p>The Field or .tvf file.</p>
                  <p>This file contains, for each field that has a term vector stored, a list of
                  the terms and their frequencies.</p>
                  <p>Field (.tvf) --&gt; TVFVersion&lt;NumTerms, NumDistinct, TermFreqs&gt;<sup>NumFields</sup></p>
                  <p>TVFVersion --&gt; Int</p>
                  <p>NumTerms --&gt; VInt</p>
                  <p>NumDistinct --&gt; VInt -- Future Use</p>
                  <p>TermFreqs --&gt; &lt;TermText, TermFreq&gt;<sup>NumTerms</sup></p>
                  <p>TermText --&gt; &lt;PrefixLength, Suffix&gt;</p>
                  <p>PrefixLength --&gt; VInt</p>
                  <p>Suffix --&gt; String</p>
                  <p>TermFreq --&gt; VInt</p>
                  <p>Term
                      text prefixes are shared.  The PrefixLength is the number of initial
                      characters from the previous term which must be pre-pended to a
                      term's suffix in order to form the term's text.  Thus, if the
                      previous term's text was "bone" and the term is "boy",
                      the PrefixLength is two and the suffix is "y".
                  </p>
                </li>
              </ol>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                    <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#828DA6">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Deleted Documents"><strong>Deleted Documents</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>The .del file is
                    optional, and only exists when a segment contains deletions:
                </p>
                                                <p>Deletions
                    (.del)    --&gt; ByteCount,BitCount,Bits
                </p>
                                                <p>ByteSize,BitCount    --&gt;
                    Uint32
                </p>
                                                <p>Bits        --&gt;
                    &lt;Byte&gt;<sup>ByteCount</sup>
                </p>
                                                <p>ByteCount
                    indicates the number of bytes in Bits.  It is typically
                    (SegSize/8)+1.
                </p>
                                                <p>
                    BitCount
                    indicates the number of bits that are currently set in Bits.
                </p>
                                                <p>Bits
                    contains one bit for each document indexed.  When the bit
                    corresponding to a document number is set, that document is marked as
                    deleted.  Bit ordering is from least to most significant.  Thus, if
                    Bits contains two bytes, 0x00 and 0x02, then document 9 is marked as
                    deleted.
                </p>
                            </blockquote>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                                <table border="0" cellspacing="0" cellpadding="2" width="100%">
      <tr><td bgcolor="#525D76">
        <font color="#ffffff" face="arial,helvetica,sanserif">
          <a name="Limitations"><strong>Limitations</strong></a>
        </font>
      </td></tr>
      <tr><td>
        <blockquote>
                                    <p>There
                are a few places where these file formats limit the maximum number of
                terms and documents to a 32-bit quantity, or to approximately 4
                billion.  This is not today a problem, but, in the long term,
                probably will be.  These should therefore be replaced with either
                UInt64 values, or better yet, with VInt values which have no limit.
            </p>
                            </blockquote>
        </p>
      </td></tr>
      <tr><td><br/></td></tr>
    </table>
                                        </td>
                </tr>

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                    Copyright &#169; 1999-2004, The Apache Software Foundation
                    </em></font></div>
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